Related Field
The subject matter discussed herein relates generally to composite panel materials for use in walls and other articles, and is particularly concerned with a panel structure with a foam core and methods of manufacturing sports products such as paddles, bats, skateboards, wakeboards, surfboards and the like from such panel structures, as well as wall panels, dividers and other articles.
Related Background
Panel materials of various types are known for use in articles such as sports equipment including paddles or bats for use in various ball sports, skis, surfboards, skateboards, wakeboards, and the like, as well as in construction of interior walls, barriers, furniture, room dividers or partitions, vehicle walls and doors, display panels, and the like, all of which require high strength to weight properties.
Sports paddles for use in playing paddleball, pickle ball, table tennis, padel tennis, smashball, and the like include a frame with a head portion. A face surface for the paddle can be made together with the frame or in a multiple step process to create the hitting surface area. The head portion surrounds and defines the hitting area. During play, the face surface is designed to contact and rebound a game piece such as a racquetball, tennis ball, or pickle ball.
Traditionally, the frames of sports paddles were made of wood. More recently, frames and paddles have been made from aluminum core, foam core, honeycomb structure core, and composite materials. In a more traditional wood or aluminum structure, the paddle is made entirely using these materials, which are cut to the desired finished shape. To complete the paddle a handle is then built up using additional wood, aluminum or other materials to increase the circumference of the handle. This process limits the weight to strength ratios as well as the ability to customize weight, balance, and the like. Traditional paddles are made of solid wood, injected plastics, or composite fiber with honeycomb cores. All of these paddles have tremendous disadvantages due to the construction methods and the limits due to the materials and technology. The paddles of today rely on these homogeneous structures that limit the weight distribution and overall weight, leaving them with limited performance characteristics. Further, the more advanced paddles with honeycomb cores are also limited due to how the panel is cut, which leaves the core edges exposed with a gap between the top and bottom surface panels. The gap allows for easy destruction of the paddle, so a plastic cover is normally added around the edges creating a step around the edges which results in a non-uniform edge. As a result, if the ball strikes the edge, it will change direction. Yet another problem with the paddles of today is the handle. The handle is also a buildup of different materials from the surface and requires additional processing to complete. The appearance is a non-esthetic assembly of various pieces. Yet another problem with solid sports paddle construction is the sound produced at ball impact. The core is usually made of an entirely rigid material giving out loud sounds on impact. Cores or other dampening material are not added due to the weight restrictions or difficulties in manufacture.
Solid face hitting areas are often made from wood and aluminum alloy materials. Due to the ease of manufacturing these structures, solid wood or aluminum structures have been used to produce low price, low technological, and mass-production frames. These solid face structures have many limitations, mostly due to the materials and limited use of these materials. The frame and solid face structures cannot be manipulated to increase strength, stiffness, or change the shape of said structures. Additionally, wood and aluminum structures are heavy and lack strength.
Currently, composite frame and face structures are used in paddle manufacture, mostly because of the higher strength-to-weight ratio in composite paddle frame and face construction. Combinations of materials such as carbon, para-aramid fiber, fiberglass, boron, and other fibrous material have been used to manufacture sports paddles in recent years. This can produce paddles that are more rigid, lighter, and larger, thus improving the player's ability and advancing the evolution of each individual sport.
Paddle frames of composite paddles are sometimes produced by bladder molding where a structure is created by using compressed air, chemical reactions to increase pressure, or hot gases to apply internal pressure within the structure, thus forcing the material to the predetermined edges of the rigid mold shape. At the same time, when pressure is added to the structure, the mold and the part is heated to a temperature which that accelerated the catalyst process to harden the structure. Once hardened, usually using thermal set resins, a rough paddle frame structure is created.
The first step in bladder molding is to prepare the part for the molding process. The step is called creating a “pre-shape”. A pre-shape is a straight tube structure. The part is shaped and formed later to produce a structure with outer dimensions matching that of the inner mold cavity dimensions. A rigid mandrel is used to create a predetermined shape. A nylon bladder is placed over the mandrel. This nylon bladder is sealed to contain the air, chemical or hot gas pressure. The layup process for the outer frame then begins on the rigid mandrel with the bladder in place.
The lay-up process is the application of multiple plies of carbon, Kevlar, fiberglass, and other synthetic and natural fibrous materials. Once the lay-up is completed, the pre-shape is placed into a mold having a special design. To create paddleball racquets, pickle ball paddles, and other solid face game paddles, an additional step is required to complete the lay-up process. The building of the face or striking surface is a process in which the lay-up of the frame structure and face structure are combined to make a single structure.
The building of the face structure or striking surface requires a combination of carbon, para-aramid synthetic fiber, fiberglass, and other synthetic fibrous materials, usually with a continuous foam core to fill the space between the front striking surface and opposing back striking surface. A gap ranging from ¼″ to 2″ is common in the building of today's paddles or racquets. The materials used to fill the space between the two surfaces can significantly increase the weight of the paddles, thus requiring reduction of the number of plies used on the frame structure or striking surface. This significantly reduces the overall strength as well as strength to weight ratio of the paddles.